Electric switch for heavy electric currents



July 8, 19% 1,560,847

M. RALL ET AL ELECTRIC SWITCH FOR HEAVY ELECTRIC GURRENTS Filed Feb. 10, 1922 Patented July 8, 1924.

UNITED STATES PATENT OFFICE.

1MAX BALL AND QTAIEB, OF STUTITGABT, GERMANY, ASSIGNORS 1'0 ROBERT BOSCH AKTIENGESELLSCHAFT, .OF S TUT TGART, GERMANY.

, "ELECTRIC SWITCH HEAVY'ELECTBIG GUB-BENTS.

Application filed February 10, 1922. Serial No.- 535,550.

T 0 all whom it may concern:

Be it known that we, MA BALL and Bonner MAIER, both citizens of Germany, residing at Stuttgart, Germany, have invented certain new and useful Improvements in Electric Switches for Heavy Electric Currents, of which the following is a specification.

This invention relates to electric switches intended for heavy electric currents and of the general type employing a switch bridge movable toward and from spaced stationary contacts, the switch bridge having metal brushes and also spring-pressed carbon brushes that are conductively connected with each other and project slightly beyond the contact surfaces of the metal brushes so as to efiect the first contact onthe closing movement of the switch bridge and the final interruption of the circuit on the opening movement of the switch bridge.

Our invention relates more particularly to certain improvements in switch bridges of the type shown in the patent to Kratz 1,311,974, dated August 5, 1919. With the known switch bridges, of the type shown in the aforesaid patent to Kratz, the carbon contacts are attached to plate springs which conduct the current, and there may be special steel plate springs increasing the strength of the elastic pressure to which the carbon contacts are subjected when in enga gement with the stationary contacts of theswitch. This arrangement does not re main effective for its intended purpose under all conditions of use, because at rather great intensities of current and upon a rather prolonged closure of contact the comparatively thin springs become heated to their glowing point and lose their elasticity.

The present invention relates to a switch bridge in which the before-mentioned drawback is obviated by providing arigid carrier .of conductive material and of relatively large mass and surface area for the carbon contacts, which carrier is guided upon the switch spindle and is itselfsubjected to an elastic pressure.

As, with this construction, direct contact of the springs with the highly heated carbons is avoided, the springs engaging the rigid carrier only there is not that conduction of heat from the carbons to the springs occurring in the known arrangement. To further les en the on ct on of he t the springs, our invention contemplates an arrangement providing for the engagement of the springs with the carrier only at points relatively remote from the carbons. Fur thermore, the carrier may have a large sectional area for the current and a great radiating surface whereby the springs are especially effectively protected from undue heating. In order to permit of adjusting the carbon contacts into any position, the carrier in which they are mounted is preferably loosely guided upon the switch spindle.

In order to make our invention more clear, we refer to the accompanying drawing which shows, by way of example, one form of construction of the improved switch bridge, and in which similar nu merals of reference denote similar parts throughout the several views. Figure 1 is an axial section through the switch brid e, and Fi ure 2 is a plan of the same. The switch bridge consist-s of the metal brushes 3 which bridges the stationary contacts 1 and 2. The carbon contacts 4 and 5 are affixed to a carrier 6 loosely guided upon the spindle 7. The carrier 6 is acted on by a plate spring 8. The carrier 6, in the example shown, is disk or plate-shaped in order to have a large radiating, i. e. cooling, surface. The size of the carrier renders possible the employment of a comparatively extended spring 8 of the configuration shown. This spring contacts with the carrier only at two oppositely disposed points from the. two oppositely disposed carbon contacts i and 5, measured along the periphery of the carrier '6, and

which points are therefore at the maximum possible distance from the carbons iand 5. To provide for the limited contact referred to of the spring 8 with the carrier 6, oppositely disposed ridges 9 may be formed either by appropriate bulgings of the spring 8 or by lugs upon the plate 6. The object of guiding the carbon carrier loosely upon the switch spindle is to allow of the surfaces of the carbons accommodating themselves more easily to the contact surfaces 1 and 2.

Having now described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A switch bridge for heavy electric currents comprising, combination, a switch spindle,'a conductive bridge member mounted thereon, metal brushes carried by said bridge member, a rigid conductive carrier member guided for movement in opposite directions'upon said spindle, contacts upon said carrier member extending substantially in the direction ot'said brushes and adapted in one direction of movement said carrier member to be projected beyond the terminal faces or" said brushes, and a spring arranged to press said carrier member in the direction projecting said contacts.

2. A switch bridge for heavy'electric currents comprising, in combination, a switch spindle, a conductive bridge member mounted thereon, metal brushes carried by and" extending from one face ofsaid bridge member, conductive and disk-shaped rigid carrier loosely mounted on said spindle for movement in opposite directions therealong tov-rard and away from said bridge member, carbon contacts on said carrier extending substantially in V the direction of said brushes, said carrier being arranged for movement in one or said directions to project said carbon contacts beyond said brushes'and for movement in the opposite 7 direction to retract said carbon contacts and a springpressing said carrier in the direc tion to project said contacts.

3. A switchbridge for heavy electric currents comprising, in combination, a switch spindle, a conductive bridge member mounted thereon, metal brushes carried by and extending from one face of said bridge member, a conductive and dis r-shaped rigid carrier member loosely mounted on said spindle for movement in opposite directions toward and away from said br dge'member and having spaced carbon contacts extending substantially in the direction of said brushes, said carbon contacts being adapted in one of said directions of movement of said carrier to; be projected beyond the terminal faces of said brushes and a spring member mounted on said spindle and enaging said carrier at opposite points spaced maximum distance fromrsaid carbon conts to press said carr er in the direction 7 pro ect said carbon contactsbeyond' said In electric switch for heavy currents, the combination with spacedsstationary contact members, ofa conducting bridge adapted tor'perpendicular switching mo ments relative to said stationary contact members and comprising a spring-plate member provided with contacts for engagement with said stationary contact members,

arran ed to Jress said carrier member toward said spring-platemember.

5. In an electric switch for heavy currents, the combination with spaced stationary contact members, of a conducting bridge member adapted for perpendicularv switching movements relative to said stationary contact'members and comprising a spring plate member having metal brushes extending substantially in the direction of the switching movement, and a conducting circuit-breaking member having contacts at its ends normally projecting beyond said metal brushes toward said stationary contact members, said circuit-breaking member comprising a rigid contact carrier, means mounting said contact carrier on said spring-plate member for independent vertical movement and a spring arranged to-press said carrier member toward said spring-plate member. 6. In an electric switch for heavy currents, the combination with spaced station ary contact memberaof aconduct-ingbridge adapted for perpendicular switching movements relative to said stationary contact members and comprising a spring-plate member provided with metal brushes for to said springplate member, wlierebyin the V perpendicular movements of said bridge said contacts on said carrier engage said disengaged therefrom later than the respective engagement and disengagement of said signatures in presence of two witnesses;

MAX BALL. ROBERT MAIER- Witnesses:

' PAUL SCHMIDT, HELMA RANDER.

stationary contact membersearlier and are 

